Rotary Phase Converters: Single Phase to True Three Phase

How a rotary phase converter works

A rotary phase converter turns the single-phase power you already have into true three-phase power. A heavy idler motor (the generator) spins up on your single-phase supply and generates the third leg. The result is balanced three-phase power on all three legs, so your machines run at full rated horsepower. That's why rotary converters run CNC machines, compressors, HVAC, welders and whole machine shops where a static converter or a VFD can't.

Sizing a rotary phase converter by horsepower

Start with your largest motor. For standard loads, pick a converter about twice the horsepower of that motor. A GP10NL, for example, runs 10 HP in total and starts a single motor up to 5 HP. For hard-starting loads such as compressors, HVAC and high-inertia equipment, start at 2.5 times the largest motor. Running several machines at once? Add up everything that runs at the same time. Not sure? Call 800-417-6568 for free sizing from a phase-conversion specialist, not a call center.

NL, PL or DualZone?

• NL (Standard): the workhorse. Reliable three-phase power for shops and CNC, 3–100 HP.
• PL (Premium): adds magnetic starter controls (start/stop) and voltage-monitor protection.
• DualZone (Auto-Zoned): two precision-balanced idler motors that start one after the other to soften the starting surge. More generating capacity than a single-idler unit of the same rating, for big shops and multi-machine loads, 10/20 to 100/200 HP.

Built in the USA since 1968

Every Phoenix rotary phase converter is assembled and tested in Phoenix, Arizona. Each one has a TEFC cast-iron idler motor and a NEMA 4 indoor/outdoor enclosure as standard, a lifetime generator warranty, and full wiring diagrams. Most units ship in 1–2 business days from U.S. warehouses.

Rotary phase converter FAQ

What is a rotary phase converter?
A machine that uses a spinning idler motor to turn single-phase power into true, balanced three-phase power, so three-phase equipment runs at full rated horsepower.

What size rotary phase converter do I need?
For standard loads, about twice the HP of your largest motor. For compressors, HVAC and other hard-starting loads, about 2.5 times. Call 800-417-6568 for free sizing.

Rotary vs. static vs. VFD: which is better?
A static converter only helps a motor start, then runs it on single phase at about two-thirds of its power. A VFD runs one motor. A rotary converter makes real three-phase power for several machines, including CNC.

Can a rotary phase converter run a CNC machine?
Yes. Balanced output on all three legs is what CNC controls and drives need. We size for the whole machine, not just the spindle.

What's the difference between NL, PL and DualZone?
NL is the standard model. PL adds magnetic starter controls and voltage-monitor protection. DualZone uses two idler motors for more capacity and a softer start on large loads.

Where are Phoenix rotary phase converters made?
Assembled and tested in Phoenix, Arizona, with a lifetime generator warranty.